Mackensen. From there to the delta of the Maritsa the front was guarded by the Bulgarian Second Army and the independent 10th Aegean Infantry Division. The Bulgarian High Command realized the difficulties involved in holding such a long front and planned measures to improve the situation. The expected entry of Romania in the war on the side of the Entente provided an additional incentive and an eventual German blessing for a Bulgarian offensive on the Macedonian front. The plan was to strike on both Allied flanks in order to cut their communication lines with the Italians in Albania and seize the Drama – Giumurdzhina railway. The second objective was given to the Bulgarian Second Army and the 10th Aegean Division. For the operation general Todorov could rely on 58 battalions, 116 machine guns, 57 artillery batteries and 5 cavalry squadrons in his army and an additional 25 battalions, 24 machine guns, 31 batteries and 5 squadrons in the 10th Division. The Struma Offensive began on 18 August with the 7th Rila, 11th Macedonian Division and the 3/2 Infantry Brigade and 10th Division advancing on a 230-kilometer-long front. For 6 days the Bulgarian forces achieved all their objectives in the face of weak Greek and French resistance. The depth of the advance reached 80–90 kilometers and an area of 4,000 square kilometers was occupied. Most importantly, however, the Macedonian front was shortened with 100–120 kilometers and the Greek IV Army Corps, that was positioned in the area, was disbanded, its troops and armament interned by the Germans in Silesia. On the right Bulgarian flank, however, the advance of the Bulgarian First Army soon stalled and was called off. The Entente now planned an offensive against it in order to support the hard pressed Romanians and knock out Bulgaria out of the war. While the main blow was directed against the First Army the British were tasked with secondary operations against the Bulgarian second Army that were designed to pin down as many Bulgarian troops as possible. In the middle of September, as the situation of the Bulgarian First Army deteriorated, the commander of the Bulgarian Second Army general Todorov ordered the 7th Rila Division to take positions for an attack over the Struma river, in order to assist the hard pressed Bulgarians and Germans west of the Vardar. The Bulgarian high command, however, refused to give permission for the attack. This